Reusing sterile cotton fabric barriers in the clinical practice: an observational and longitudinal study

Objective: to analyze the physical and biological barrier characteristics of cotton fields used as a sterile barrier system after multiple use and processing cycles in the clinical practice. Method: an observational and longitudinal study to monitor and evaluate 100% cotton fabric used as a sterile barrier system in a medium-sized hospital. Samples were collected before use (after three washes) and at three, six, nine, 12 and 15 months of use and evaluated for the number, thickness and integrity of threads, weight, water absorption and wet penetration by microorganisms. Results: after 85 washes, the number of threads remained unchanged, and the shredded fibers and the water volume absorbed were increased. The microbiological test using the German standard methodology obtained a negative result and wet penetration by microorganisms did not show significant changes over time, although a percentage of the microbial cells passed through the double-layer samples. Conclusion: the physical properties of 100% cotton used as a sterile barrier system changed with use/processing cycles; however, these alterations did not significantly interfere with the results obtained by the tests performed on the microbiological barrier up to 85 washes.


Introduction
Health Products (HPs) classified as critical and used in invasive procedures must be subjected to sterilization.
It is a process capable of destroying all forms of microbial life (1) , whose most commonly used method is Saturated Vapor under Pressure (SVP).To preserve sterility, HPs should be packed in a Sterile Barrier System (SBS) for storage.
In Brazil, choice of the SBS used for this purpose must be regularized with the National Health Surveillance Agency (Agência Nacional de Vigilância Sanitária, ANVISA), Collegiate Board Resolution (Resolução da Diretoria Colegiada, RDC) No. 15, of March 15 th , 2012 (2) .This resolution provides that the SBS must offer an efficient barrier against microorganisms, particles and fluids in order to allow an aseptic presentation of the HPs and enable proper delivery of the content, preserving them from possible contamination.

SBS indicated for SVP sterilization are classified
into disposable (surgical grade and creped papers and non-woven fabrics) and reusable (cotton fabrics and rigid containers).Cotton fabric has been one of the oldest and most used worldwide until the emergence of non-woven fabrics; its use in Brazil is recommended and remains common in health institutions, although it has not been subject of studies in the last decade (2)(3) .100% cotton fabric in health institutions is not only used as SBS, but also for making aprons and surgical fields (4) .A recent study that compared the cotton fabric of surgical aprons to disposable fabrics concluded that adopting reusable aprons can result in greater protection and significant cost savings due to their superior durability and sustainability when compared to disposable items (5) .
To use the fabric, it is recommended to apply it in double layers or in a mixed modality, that is, a layer of fabric and another disposable SBS (6) and, after each use, it must be washed to remove dirt resulting from storage, transport and use and to restore hydration of the fibers (3) .However, it is understood that the friction to which they are subjected, the cleaning products used and the temperature variations during sterilization, among other elements during processing, may result in variations in their ability to resist penetration by microorganisms according to the number of uses and wash and sterilization cycles (7) .In this sense, some studies have investigated durability and loss of the microbiological barrier of cotton fabric SBS in Brazil; however, their findings are divergent regarding the ideal number of processing cycles (washing and sterilization) safe for use (8)(9) .In addition to that, there are difficulties in reliably recording the processing frequency of each surgical textile (10)(11) .
Considering the lack of consensus regarding the safe number of use and processing cycles and the challenges to evaluate maintenance of the cotton fabric properties for health institutions and professionals, especially of Technical Standards (Associação Brasileira de Normas Técnicas, ABNT) -Brazilian Standard (Norma Brasileira, NBR) 14,027/9 (12) , of the Santista ® brand and classified by Solasol in royal blue color (518/193952TC D), 100% cotton, texture of approximately 39.63 threads per square centimeter (cm 2 ), weight of 260 grams per square meter (g/m 2 ) and 3/1 twill ligament.Although this standard indicates 2/1 ligaments, a 3/1 presentation was used to achieve the recommended weight.
In each piece, a chart containing 120 spaces was printed in order to monitor the number of washes to which it would be subjected.Thus, when receiving the laundry fields, in the CSSD area devoted to folding, the nursing technician filled a space with black indelible pen (13) .The stage was monitored daily by a researcher and/or research assistants (two), previously trained, during the 15-month study period.Before the first use, the new fields were washed three times to remove the starch.

Data collection
Samples for the analyses were collected at the CSSD folding area when the textiles were received from the laundry, selecting three different fields (one sample was cut from each of the three fields) at each collection, selecting those that contained the record of the largest number of washes.The collection moments were as follows: "Zero" time: after the third wash and before the first use; Time 1: with three months of use; Time All new fields were washed three times before the first use to remove the starch used in the ironing process by the manufacturer.Three fields were randomly selected at this stage as samples for the Control Group (not subjected to use/processing cycles).

Ethical aspects
The study was approved by the Ethics Committee of the Federal University of Goiás (Certificate of Presentation for Ethical Appraisal Protocol No. 64541517.3.0000.5083)and had the consent of the hospital management and the technicians responsible for the CSSD and the Surgical Center (14) .

Results
The mean washings of the cotton fields used with SBS in each study period were as follows: 24 times -three months; 42 times -six months; 57 times -nine months; -70 times -12 months and 85 times -15 months.Rev. Latino-Am.Enfermagem 2023;31:e3990.
The weight assessment related to size (g/m 2 ) of the fields before and in subsequent use periods, in months, showed that there was progressive dimensional shrinkage in all fields and, in parallel, an increase in weight up to three months of use, of 1.1% (g/m 2 ), when compared to those unused.After this period, a gradual 5.9% (g/m 2 ) reduction was verified up to 15 months of use (Table 1).
The analysis performed to verify the number of threads in the warp and in the weft of the samples presented no changes, remaining at 40 threads per cm 2 .
However, the longer the use time, the higher the number of fibers of the fabric threads shredded, as can be seen in the images of the samples obtained by means of SEM, shown in Figure 3.
Thickness of the threads in the weft of the threemonth samples presented a 187 µm (-18.6%)decrease in relation to the samples before the first use (three washes).
At 12 months (M: 70 washes), a 299 µm (-29.8%)reduction was observed; this result was statistically significant (Table 1).There was a statistically significant difference in the water absorption volume between the samples before the first use and those with three, six, nine, 12 and 15 months of use (Table 1).However, the difference between the water absorption volumes in the time intervals after use was not statistically significant.
The results of the microbial tests according to the DIN methodology showed that the percentage of cells that passed through the cotton fabric field was 0.002% (2 CFUs/10 5 cells) at the most, considered negative (<5 CFUs), which means that all samples met the test requirements both for single and double fabric samples, as shown in Table 1.
The penetration by microorganisms analysis by means of SEM of double fabric samples (Table 1) revealed that there was transfer of bacteria in the tested samples from all periods analyzed in the study.The mean number of bacteria seen increased proportionally to the use time These results did not present any statistically significant difference.

Discussion
The analysis of the fields used as SBS, in clinical use and control of the number of use and processing cycles, evidenced that there was an increase in weight (g/m 2 ) up to three months of use, despite dimensional shrinkage, when compared to the unused fields.In addition, after this period, a gradual loss was verified up to 15 months of use.These results are similar to those of an experimental study that followed the phases of washing and sterilization Bowman BE, Costa DM, Tessarolo F, Tipple AFV.
of fields for double cotton SBS and where the samples (100 cm 2 ) showed increased weight (g/m 2 ) up to the 25 th wash and, subsequently, a gradual decrease up to the 75 th (9) ; they also match another research study (4) , carried out with 100% cotton fabric samples from surgical fields and aprons with the same characteristics of this study and subjected to multiple use and processing cycles in the clinical practice.
Another study was carried out in a Basic Health Unit (BHU) with cotton fabric fields used in the Unit as SBS, from three manufacturers; the fabric was processed in commercial washers and dryers and sterilized in a saturated steam autoclave under 21 liter pressure.
Samples (4 cm 2 ) subjected to 65 processing cycles were evaluated, which evidenced that the samples from two manufacturers (2x1 ligaments/weft) presented a reduction in weight (g/m 2 ), whereas those from one manufacturer (3x1 ligaments/weft) showed an increase (15) .
Regarding the weight loss of the textiles, another study (9) , in which the fields were processed in a hospital washer, centrifuge and dryer by a third-party company and not used in the clinical practice, the mean loss that began after the 25 th wash was 5.1% after 65 washes.
In another study (15) , where the fabrics were processed in a commercial washer and dryer and used as SBS (simple fields), weighing more than 210 g/m 2 (12) .It is noted that this property was tested exclusively in the fabric evaluated in this study, not allowing to infer the same for other textiles, although it is presumable for those that follow the same specifications.
The longer the use time and number of washes of the fields used as SBS, the higher the number of shredded and loose fibers.Despite the damages to the structure, it was evidenced that there was no change in the number of threads, both in the warp and in the weft, up to 15 months of use and 85 washes.Similar results were reported in a study conducted with cotton fabric masks (16) .
The aforementioned study (15) , carried out in a BHU, also analyzed the number of shredded and loose fibers, presented similar results and evidenced maintenance of the number and a reduction in the thickness of the threads and an increase in detachment of fibers from double cotton fields from three manufacturers, after 65 processing cycles (washing and sterilization).It also verified that there was a difference in degradation performance between the evaluated samples from the same manufacturer and from one manufacturer to the other.
It is also worth noting that, despite the physical changes identified by the analytical tests, all samples were visually intact and none had mending, which are minimally expected conditions for the useful life of a 100% cotton fabric SBS.These facts reinforce the importance of these indicators in defining the finitude of this type of SBS in the care practice.
Water absorption was higher in the samples that had three months (24 washes) when compared to those before the first use (three washes).Considering that SVP sterilization, a method to which HPs packed with cotton SBS are subjected, this result favors the prerogative of a barrier system that should allow penetration and removal of the sterilizing agent during the sterilization process (2)(3) .However, it is recommended that, at the end of the sterilization cycle, the packages be dry and stored in clean and dry places, handled as little as necessary, and that the storage conditions are periodically inspected in order to maintain sterility (1,17) .Therefore, this result reinforces the disadvantage of cotton fabric's low repellency to liquids (3) , an aspect that deserves to be further investigated.
Based on the prerogative that the fabric fields used as SBS of HPs should guarantee sterility of these products during the storage period, in the 1990s, in the Manual of Processing for Articles and Surfaces in Health Services (18) , the Ministry of Health recommended a shelf life of seven days for the storage of HPs packed in cotton fabrics, which could be extended by validating the storage conditions of each service.In this sense, studies that aimed at analyzing how sterility of HPs is maintained and, therefore, the barrier offered by cotton fabric as SBS, obtained results that extended the period recommended in that manual.
A survey (19) that evaluated SPV-sterilized HPs packed in cotton fabric concluded that, after 25 days of storage under controlled conditions, there was no microbial growth in the HPs.Another two studies (20)(21) evidenced that the 100% double cotton fabric maintained sterility of the HPs for periods of 148 and 18 days, respectively.It is noted that the most current recommendations regarding the storage time for HPs subjected to sterilization consider that the period must be based on the SBS custody and integrity conditions (1,3) .
a broad approach with multiple analytical tests.Another limitation was the use of originally developed tests instead of standardized methodologies.This approach allowed for a more precise quantitative comparison between the test and control groups, whereas standard tests are better suited to verify compliance with prerequisites, oftentimes using a qualitative approach.
The results of this study cannot be extended directly to other fabric compositions and further studies are required to evaluate the effect of alternative methods and technologies for processing reusable fabrics.

Conclusion
It is concluded that fields intended for SBS, made of showed that no significant degradation of the microbial barrier properties was observed over time.
nurses (historically the technical professionals in charge of the Central Sterile Supply Department [CSSD] unit), the following guiding question was established for this study, a pioneer in the evaluation of the properties of cotton fabrics used in the clinical practice: Are there changes in the physical characteristics and biological barrier of 100% cotton fabric fields used as sterile barrier systems subjected to multiple use and processing cycles in relation to new ones?And, as objective: to analyze the physical and biological barrier characteristics of cotton fields used as sterile barrier systems after multiple use and processing cycles in the clinical practice.Method Study design A longitudinal and observational study to monitor and evaluate SBS samples made with 100% cotton fabric and used in the clinical practice, during a 15-month period.The Strengthening the Reporting of OBservational Studies in Epidemiology (STROBE) guide was used to report the research.Context The study was carried out between February 2018 and May 2020 in a medium-sized philanthropic hospital (n=60 beds) from Jataí, Southwest region of the state of Goiás (GO), Brazil.Samples of 100% single and double cotton fabric from fields used as SBS, new and after subsequent processing cycles, were analyzed.The samples were analyzed in the Bacteriology and Mycology Laboratory of the Biomedicine Course at the Federal University of Jataí and in the Department of Medicine Laboratory, Provincial Health Services Trust of Trento/Italy -Santa Chiara Hospital -Trento, Italy.Definition of the samples Based on the demands of the institution's surgeries (mean of 101 monthly surgeries), 104 100% new cotton fabric fields [1.20 meters (m) x 1.20 m] were made, plus 30% for replacements during the research (31 fields).The fabric used met the standard of the Brazilian Association Bowman BE, Costa DM, Tessarolo F, Tipple AFV.

2 :
with six months of use; Time 3: with nine months of use; Time 4: with 12 months of use and Time 5: with 15 months of use.

Figure 1
Figure 1 represents the study design from the preparatory phase, collection period and number of samples and analytical tests performed to data analysis.

Figure 2 Figure 1 -Figure 2 -
Figure2shows the analytical tests performed, the place where they were applied, and the number, size, shape and fabric layers of the samples.

*
Figure 3 -Images obtained by means of Scanning Electron Microscopy of samples of 100% cotton fabric fields intended for sterile barrier systems before and in subsequent use periods, in months [three (Mean -M): 24 washes), six (M: 42 washes), nine (M: 57 washes), 12 (M: 70 washes), 15 (M: 85 washes)] at a medium-sized general hospital.Jataí, GO, Brazil, 2018-2020 until the sixth month (mean of 42 washes), when it presented the highest penetration number, with a mean of 17 bacteria.The samples at nine months (mean of 70 washes) and 12 months of use (mean of 85 washes) presented lower mean bacteria values: ten and eight.
in a BHU, the mean weight loss of the fields from two manufacturers was 0.1% and 0.5% after 65 washes, respectively.Values lower than the one found in this paper (mean of 8.4%), whose fields used with SBS underwent processing in a washer, centrifuge and dryer (15 months of use, mean of 85 washes) showed that there was greater wear out of the fabrics used in the clinical practice at the hospital.Despite the mean 8.4% reduction in the weight of the fields in this research, the fabric presented compliance regarding the minimum weight established byNBR 14,027 In this sense, by contributing to defining minimum indicators for the use and reuse of SBS made of 100% cotton fabric and their sizing in health services, this study also contributes to the work process of Nursing teams, which are the main players in CSSDs, especially in Brazil.Additionally, it is relevant for the nurses who make up the Committee on Processing of Health Products and the Commission on Healthcare-Associated Infections.

100%
cotton fabric, did not change the number of threads of the samples after use and the repeated washing and sterilization processes; however, there was impairment of the fabric's physical structure, shown by the increase in the number of shredded fibers of the threads and in the mean volume of absorbed water.While a significant change in the fabric's physical properties has been documented over the 15 months of clinical use and processing cycles, the microbiological tests

Table 1 -
Comparative synthesis of the results obtained from analytical tests for the characterization of 100% cotton fabric fields employed as sterile barrier systems, unused (Control Group) and used in different use/processing time periods in the clinical practice.Jataí, GO, Brazil, 2018-2020

Samples used and processed* † % changes in relation to the unused samples Variable trend ‡ Sample use time (months)
*Values expressed as median (first quartile-third quartile) of the distribution corresponding to the experimental values; † Values are reported in bold when significantly different from the Control Group, p<0.05; ‡ Qualitative comparison corresponding to the values of the variables over the entire life cycle of the device: ↑ increase; ↔ unchanged; ↓ decrease; § The 6000× view field corresponded to an area of 0.00213 mm 2